We will investigate newly discovered short-latency disparity vergence responses DVR) in strabismic subjects with deficient, but present, binocular function (BF). BF is usually measured with subjective (rather than objective) tests. Lack of objective measures of BF fundamentally affects our understanding of the neuropathogenesis of strabismus and development of binocular vision. DVR are reflexive eye movements resulting from binocularly processed visual signals (binocular disparity) shared with stereopsis. Studies have shown that DVR can be elicited in normal subjects, and DVR are dependent on disparity, but it is not known if DVR are affected by defective BF in strabismic subjects, and if so, does the dependence of DVR on disparity still exist, and how it is modulated by defective BF? In an attempt to investigate the above issues, we formulated our proposal. The central hypothesis of our proposal is that DVR in strabismic subjects are correlated with their deficient BF. A series of clinical tests will be used to evaluate the BF in subjects with monofixation syndrome (MFS). Large-field random dot patterns displayed on monitors and controlled by computers will be used to provide binocular disparity. A magnetic scleral search coil system will be used to record DVR eye movements. We will identify the relationship between horizontal DVR and disparity, and analyze the relationship between vertical DVR and horizontal simulated tropias in controls and in patients with MFS, and finally correlate DVR with deflective BF. Gabor Function and Gaussian Function will be used to characterize the relationship between DVR and disparity, as well as simulated tropias. MANOVA statistical analysis will be performed to examine the difference in DVR between controls and patients. Correlation between DVR and BF will be tested with Multiple Linear Regression. A positive correlation between DVR and BF will help us to better understand the role of DVR in binocular vision. The proposal has the potential to help develop a new methodology to study the neuro-pathogenesis of strabismus. The rapid, reflex-like nature allows objective assessments of binocular function for potentially all age subjects since active visual attention is not required and promises for future studying of the development of binocular vision.